Optical properties of glasses (TeO2–GeO2–K2O) thin films co-doped with rare earth oxides Sm2O3/Yb2O3

Abstract: Glassy thin films of [TeO2–GeO2–K2O] co-doped with rare earth oxides Sm2O3/Yb2O3 were prepared by electron beam evaporation technique on polished fused silica glass substrate. The effect of Sm2O3/Yb2O3 rare earth sub-oxides co-doping on optical properties of glasses 80TeO2–10GeO2–8K2O thin films has been investigated using optical spectrophotometry measurements in the wavelength range 200–2500nm. The structural characteristics studied by X-ray diffraction (XRD) showed that all the films are amorphous. The fundamental optical parameters like band gap and absorption coefficient are calculated in the strong absorption region of transmittance and reflectance spectrum. The possible optical transition in these films is found to be allowed indirect transition with energy gap decreases from 1.27 to 1.06eV with increasing Yb2O3 at expense of Sm2O3. The decreasing in can be interpreted in terms of the non-stoichiometry of the films. The refractive indices have been evaluated in term of envelope method suggested by Swanepoel in the transparent region. The refractive index, n, can be extrapolated by Cauchy dispersion relationship over the whole spectra range. It is observed that the refractive index, n increases with increasing Yb2O3 at expense of Sm2O3 which might be related to the changes in the compositions of TeO2 and GeO2 sub-oxides in the films. [Copyright &y& Elsevier]